Tutorial / Cram Notes

Using BGP over AWS Direct Connect is an essential practice for maintaining a reliable and optimized network connection between your on-premises infrastructure and your AWS environment. AWS Direct Connect bypasses the public internet and provides a private, dedicated network connection, which, when coupled with BGP, enables dynamic routing that is secure and offers low-latency connectivity.

How BGP works with AWS Direct Connect

BGP is used over Direct Connect to exchange routing information between the AWS network and a customer’s on-premises network. This means that both networks can make intelligent routing decisions and ensure that data takes the most efficient path to its destination.

When setting up BGP over AWS Direct Connect, you’ll need to configure BGP on both the AWS side and your on-premises router. Here are the steps typically involved:

  1. AWS Side Configuration

    • Create a Virtual Private Gateway (VGW) and attach it to your VPC.
    • Create a Direct Connect gateway and associate it with your VGW.
    • On the Direct Connect gateway, create a virtual interface for your Direct Connect connection.
    • Allocate private IPs for BGP peering.
  2. On-Premises Router Configuration

    • Configure the Direct Connect router with the AWS-provided BGP peering IPs and the ASN (Autonomous System Number).
    • Set up the BGP session, specifying the BGP parameters such as the local ASN, BGP key, and MD5 hash if required.

BGP Configuration Example

For the purposes of this example, let’s consider that AWS assigned you an IP of 203.0.113.1/30 for your end of the BGP session and 203.0.113.2/30 for their end. The AWS ASN is 64512, and your ASN is 65000.

Here would be a hypothetical configuration snippet for a Cisco router:

router bgp 65000
bgp log-neighbor-changes
network 192.168.1.0
neighbor 203.0.113.2 remote-as 64512
neighbor 203.0.113.2 password MY_SECRET_PASSWORD
neighbor 203.0.113.2 timers 10 30 30

In this configuration, 192.168.1.0 represents the network on the customer’s side that they want to advertise over the BGP session. Timers have also been configured for how often BGP keeps alive and hold-down timers will check the connectivity.

Benefits of Using BGP with AWS Direct Connect

The employment of BGP with AWS Direct Connect offers numerous benefits which include:

  • Improved Redundancy: By advertising multiple routes to the same destination, BGP can provide redundancy and ensure that if one path fails, traffic can automatically reroute to another path without service interruption.
  • Route Optimization: BGP makes possible the selection of the most efficient route for traffic, which means reduced latency and potentially improved application performance.
  • Scalability: As network topologies become more complex, BGP can handle an enormous number of routes and thus is exceptionally well-suited to enterprise-level networking.
  • Controlled Routing: Administrators have fine-grained control over routing policies and can prioritize or modify the routing of traffic based on specific requirements.

Conclusion

In summary, BGP over AWS Direct Connect is essential for creating a robust, scalable, and high-performance hybrid network. By combining the low-latency, high-bandwidth benefits of Direct Connect with the dynamic routing intelligence of BGP, enterprises can ensure seamless connectivity between their on-premises and AWS environments. The result is a network architecture that supports the demands of today’s high-speed, always-on digital businesses.

Practice Test with Explanation

True or False: AWS Direct Connect supports the use of the Border Gateway Protocol (BGP) for dynamic routing.

  • True

Explanation: AWS Direct Connect supports BGP, an industry-standard routing protocol, for dynamic routing between on-premises networks and AWS.

True or False: Interior Gateway Protocols (IGPs) such as OSPF and EIGRP are used within AWS to manage routing between VPCs.

  • False

Explanation: AWS uses Border Gateway Protocol (BGP) for routing between VPCs and external networks. IGPs like OSPF and EIGRP are not used within the AWS cloud for this purpose.

Which AWS service allows you to implement industry-standard routing protocols for hybrid networks?

  • A) AWS VPN
  • B) AWS Transit Gateway
  • C) AWS Direct Connect
  • D) Amazon VPC Peering

Answer: C) AWS Direct Connect

Explanation: AWS Direct Connect allows for the implementation of industry-standard routing protocols, such as BGP, for hybrid networks between on-premises data centers and AWS.

True or False: You need to manually install and manage BGP on your AWS resources for it to work with AWS Direct Connect.

  • False

Explanation: BGP is natively supported by AWS Direct Connect, and customers configure BGP on their side of the connection; there is no need to manually install BGP on AWS resources.

What is primarily used to exchange routing information between an AWS VPC and a customer’s on-premises network in a hybrid environment?

  • A) BGP
  • B) OSPF
  • C) RIP
  • D) IS-IS

Answer: A) BGP

Explanation: BGP is the industry-standard routing protocol used to exchange routing information between AWS VPCs and customer’s on-premises networks in a hybrid environment.

True or False: You can use BGP attributes to influence routing decisions when using AWS Direct Connect.

  • True

Explanation: BGP attributes such as AS_PATH, LOCAL_PREF, and MULTI_EXIT_DISC can be used to influence routing decisions and traffic flow when using AWS Direct Connect.

Which of the following is NOT a supported BGP routing policy for AWS Direct Connect?

  • A) Prefix-based routing
  • B) Path-based routing
  • C) Bandwidth-based routing
  • D) AS_PATH prepending

Answer: C) Bandwidth-based routing

Explanation: AWS Direct Connect supports BGP routing policies like prefix-based routing, path-based routing using AS_PATH, and AS_PATH prepending. Bandwidth-based routing is not a standard BGP feature.

Multiple Select: Which of the following statements are true about AWS hybrid networking with Direct Connect and BGP?

  • A) You can connect multiple VPCs in different regions to a single Direct Connect connection.
  • B) BGP sessions only support IPv4 for routing prefixes.
  • C) BGP can advertise individual IP addresses to AWS Direct Connect connections.
  • D) IP prefixes advertised over BGP must be part of the VPC CIDR block or a part of the added secondary CIDR.

Answer: A) You can connect multiple VPCs in different regions to a single Direct Connect connection. D) IP prefixes advertised over BGP must be part of the VPC CIDR block or a part of the added secondary CIDR.

Explanation: You can use AWS Direct Connect to connect multiple VPCs across different regions. BGP supports both IPv4 and IPv6 prefixes. BGP does not advertise individual IP addresses but rather aggregate routes, and the IP prefixes advertised must belong to the VPC CIDR or secondary CIDR ranges.

True or False: With AWS Direct Connect, you can create BGP sessions for public resources like S3 and DynamoDB without using an AWS VPC.

  • True

Explanation: AWS Direct Connect supports the creation of public BGP sessions which allow access to public AWS resources such as S3 and DynamoDB without going through a VPC.

When using BGP over AWS Direct Connect, how is the Autonomous System Number (ASN) for the AWS side of the BGP session typically chosen?

  • A) It is randomly assigned by AWS.
  • B) It is always the default AWS ASN.
  • C) The customer can choose to use either the default AWS ASN or their own.
  • D) The customer must always use their own ASN.

Answer: C) The customer can choose to use either the default AWS ASN or their own.

Explanation: When setting up BGP over AWS Direct Connect, customers have the option to use the default AWS ASN or configure their own ASN for the AWS side of the BGP session.

Interview Questions

What is BGP and why is it important for AWS hybrid networks using Direct Connect?

BGP, or Border Gateway Protocol, is the standard routing protocol used to exchange routing information across the internet and between different networks. It’s important for AWS hybrid networks because when used with AWS Direct Connect, it allows for dynamic routing between an on-premises network and AWS VPCs, which can lead to more efficient use of network resources, improved redundancy, and increased network agility.

Can you explain the role of Autonomous System Numbers (ASNs) in BGP for AWS hybrid networks?

An ASN is a unique identifier used in BGP to identify each network on the internet. In AWS hybrid networks, the ASN allows AWS to distinguish among different customer networks. When setting up BGP over Direct Connect, customers can use either their private ASN or request a public ASN from AWS if they don’t have one.

How does BGP over AWS Direct Connect facilitate high availability in hybrid networks?

BGP facilitates high availability by enabling multiple redundant connections between on-premises networks and AWS. It uses its built-in protocol mechanisms to automatically reroute traffic if a link goes down, ensuring that the network remains available in the event of a failure.

What are some of the BGP attributes used in route selection that are relevant to AWS Direct Connect?

BGP attributes such as AS_PATH, LOCAL_PREF, WEIGHT, and MED (Multi-Exit Discriminator) are commonly used in route selection. These attributes help BGP to select the best path among multiple available paths, which is crucial for efficient and optimized routing over Direct Connect.

How do you configure BGP on an AWS Direct Connect gateway?

To configure BGP on an AWS Direct Connect gateway, you need to create a Virtual Interface (VIF) and then configure the BGP settings such as your peer IP, your BGP ASN, and MD5 authentication (if desired). After setting up the VIF, you would configure similar parameters on your on-premise router to match the AWS side and establish the BGP session.

In the context of AWS Direct Connect, what is the difference between a public VIF and a private VIF, and when would you use BGP with each?

A public VIF is used to access public AWS services, such as S3 or DynamoDB, over Direct Connect, while a private VIF is used to connect to private resources within a VPC, such as EC2 instances or RDS databases. BGP is used with both types of VIFs; with a public VIF, it exchanges routes pertaining to AWS public endpoints, and with a private VIF, it exchanges routes for the VPC CIDR blocks.

What is the purpose of BFD (Bidirectional Forwarding Detection) when used with BGP over AWS Direct Connect?

BFD is a network protocol used for rapid detection of failures in the forwarding path between two routers. When BFD is paired with BGP over AWS Direct Connect, it provides low-overhead, fast failure detection and aids in achieving quick failover to alternative routes, improving network resilience.

How does the concept of BGP route propagation work when integrating AWS Direct Connect with a VPC?

In AWS, BGP route propagation involves the automatic distribution of routes between a Direct Connect gateway and a VPC via a VIF. When enabled on a VPN connection or a Direct Connect gateway, it allows routes learned via BGP to be automatically propagated to the VPC route table, enabling seamless access to the on-premise resources.

What limitations should you be aware of when advertising routes over BGP with AWS Direct Connect?

AWS imposes a limit on the maximum number of routes (100 prefixes for private VIFs and 1,000 for public VIFs) that can be advertised over BGP to Direct Connect. Additionally, AWS also has requirements and best practices for BGP community tags and prefers customers to use route filtering to manage the advertised and received routes effectively.

How can you troubleshoot a failed BGP session over AWS Direct Connect?

Troubleshooting a failed BGP session involves checking the BGP configuration on both the AWS and on-premise sides, ensuring that the ASN, BGP peers, and MD5 authentication (if used) match. You should also verify that there are no underlying connectivity issues, the network Access Control Lists (ACLs) and security groups allow BGP traffic, and that the BGP timers are set appropriately for the expected hold time.

Describe how to secure BGP sessions on AWS Direct Connect.

BGP sessions on AWS Direct Connect can be secured by using MD5 authentication, which ensures that only trusted parties can establish a BGP session. Secondly, you can use BGP community tags to apply policies to route advertisements. Additionally, AWS recommends using BGP session timers to detect outages quicker, and access control mechanisms, to govern inbound and outbound traffic to the BGP routers.

Can you discuss the best practices for designing a resilient hybrid network with BGP and AWS Direct Connect?

Best practices include using redundant AWS Direct Connect connections at geographically diverse locations and configuring them in an active-active or active-passive manner. Leveraging BGP’s ability to perform route health checks and automatically failover to healthy routes is also recommended. Splitting your network traffic using multiple VIFs to isolate the traffic and potentially increase bandwidth management efficiency is another common practice.

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Deborah Morgan
5 months ago

Great post! I learned a lot about using BGP over Direct Connect in AWS hybrid networks.

Jayanth Bhardwaj
6 months ago

Can someone explain why BGP is preferred over static routing in AWS hybrid networks?

Kuno Faber
6 months ago

I appreciate the detailed explanation on how to set up BGP with Direct Connect. Thanks!

Mércia Porto
5 months ago

How does AWS handle BGP route propagation with Direct Connect?

Joanna Berger
6 months ago

The step-by-step guide for configuring BGP was really helpful!

Ingeborg Guerin
6 months ago

Is there any specific BGP parameter tuning required for AWS Direct Connect?

Ella Christensen
6 months ago

Well-explained! I now feel more confident about routing protocols in AWS.

Artemiziya Onishchak
6 months ago

I have an issue where BGP routes are flapping on my Direct Connect link. Any troubleshooting tips?

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